Data processing terminal, parent substrate, child substrate, terminal design apparatus and method, computer program, and information storage medium

ABSTRACT

A second ground plane ( 18 ); has one end opposite to a connector ( 14 ), which end is connected to a first ground plane ( 17 ) by resistor connection element ( 41 ). Accordingly, it is possible to lower Q of resonance of the ground structure by the resistor connection element ( 41 ) and to prevent generation of an intense electromagnetic field attributed to an electromagnetic field of a data processing circuit. Especially when the resistor connection element ( 41 ) has a resistance value identical to a characteristic impedance of the ground structure, the ground structure is terminated in a matched way and it is possible to assure prevention of generation of an electromagnetic field attributed to resonance.

TECHNICAL FIELD

The present invention relates to a data processing terminal whichcomprises a first and a second ground plane, a parent board and a childboard for the data processing terminal, a terminal designing apparatusand method for use in designing the data processing terminal, a computerprogram for the terminal designing apparatus, and an information storagemedium having the computer program stored thereon.

BACKGROUND ART

At present, a variety of user terminal devices are pervasive. They canserve as PDA (Personal Digital Assistant) to support a variety of users,and communicate data processed thereby to the outside using a wirelesscommunication function such as PHS (Personal Handy-phone System: aregistered trademark). Now, a prior art example of such a dataprocessing terminal will be described with reference to drawings.

FIG. 1 illustrates data processing terminal 10 as a first prior artexample. Data processing terminal 10 comprises a hollow housing (notshown) which contains parent board 11, child board 15, and connector 14for connecting both boards. Parent board 11 is mounted with a variety ofdata processing circuits (not shown) comprised of integrated circuits,while child board 15 is mounted with a memory circuit (not shown) suchas RAM (Random Access Memory), flash memory and the like.

A card slot (not shown) is formed at one end of the housing, such thatseparate card-shaped radio communication unit 12 is removably pluggedinto the card slot. Radio communication unit 12 comprises a built-inradio communication circuit (not shown), and rod-like antenna 13attached thereto.

Data processing terminal 10 has a user interface (not shown) such as atouch panel, a keyboard and the like on the surface of the housing, suchthat the data processing circuit on parent board 11 executes a varietyof data processing in response to data entered through the userinterface and the like.

In data processing terminal 10, as card-shaped radio communication unit12 is plugged into the card slot of the housing, the radio communicationcircuit in radio communication unit 12 can be in wired communicationwith the data processing circuit on parent board 11, permitting dataprocessing terminal to make radio communications in a frequency bandnear 1.9 (GHz) using a PHS function through radio communication unit 12.

In other words, data processing terminal 10 can make radiocommunications with the outside as required with the aid of radiocommunication unit 12 to transmit data processed by the data processingcircuit over the air, as well as to process data received over the airwith the aid of the data processing circuit. Further, when dataprocessed by the data processing circuit is stored in the memory circuiton child board 15, data processing terminal 10 can process a largecapacity of data.

In data processing terminal 10 as described above, parent board 11 issubstantially entirely formed with a metal-made first ground plane,while child board 15 is likewise substantially entirely formed with ametal-made second ground plane (not shown), wherein both ground planesdetermine potential references for circuits on the respective boards.

Connector 14, which connects the two boards, has a plurality of signalterminals and a plurality of ground terminals arranged in parallel,wherein one ground terminal is inserted, for example, every three signalterminals. With such a structure, as child board 15 is mounted on parentboard 11, data processing circuit on parent board 11 is connected to thememory circuit on child board 15 through the signal terminals ofconnector 14, and the first ground plane on parent board 11 is connectedto the second ground plane on child board 15 through the groundterminals of connector 14 to connect the potential references providedby the ground planes on both boards.

While FIG. 1 illustrates data processing terminal 10 which has childboard 15 mounted on parent board 11 through a pair of connectors 14 thatare removable in the vertical direction, there is also a product, dataprocessing terminal 20 illustrated in FIG. 2, which is a second priorart example, wherein child board 15 is mounted to and removed fromconnector 21 in the transverse direction.

Also, as data processing terminal 30 in FIG. 3, which is a third priorart example, there is a product which comprises connection pads 31, 32formed on the front surface and back surface of parent board 11 andchild board 15 and electrically connected to the first ground plane andsecond ground plane, respectively, with connection pads 31, 32 beingelectrically connected through tubular metal columns 34 and screws 35which make up auxiliary connecting means 33. It should be noted thatsuch metal columns 34 and screws 35 are generally intended tomechanically hold child board 15, so that they are disposed near a pairof corners at diagonal positions of child board 15.

In the aforementioned data processing terminal 10, 20, first groundplane 17 of parent board 11 and second ground plane 18 of child board 15connected through connectors 14, 21 are positioned in parallel with eachother, as illustrated in FIG. 4. Also, data processing circuit 19composed of a multiplicity of electronic parts such as LSIs (Large ScaleIntegration) and signal wires is mounted on first ground plane 17 ofparent board 11.

Since data processing circuit 19 transmits repetitive signals andnon-repetitive signals at particular frequencies within the circuit whenit processes data, an electromagnetic field is generated in theneighborhood, associated with frequency components and harmoniccomponents of the transmitted signals. This electromagnetic field notonly causes a high frequency current to flow into first ground plane 17of parent board 11 but also induces a high frequency current into secondground plane 18 of child board 15 disposed in the neighborhood.

The inventors found that the ground structure comprised of first groundplane 17 of parent board 11, second ground plane 18 of child board 15,and the ground terminals of connectors 14 as illustrated in FIG. 4 wellresembled an antenna element of a quarter wavelength resonant antennareferred to as an “inverted L-shaped antenna” or an “inverted F-shapedantenna”, as illustrated in FIGS. 5A and 5B (reference: “Small Antennas”K. Fujimoto, A. Henderson and J. R. James, Research Studies Press,Chapter 2.4).

In thinking in the foregoing manner, from the fact that connector 14comprises a plurality of ground terminals, second ground plane 18 ofchild board 15 has an edge close to connector 14 that corresponds to ashort-circuited end of the antenna element, and an edge opposite toconnector 14 that corresponds to an open end of the antenna element. Ifa current induced into second ground plane 18 from data processingcircuit 19 includes frequency components which cause second ground plane18 to generate quarter wavelength resonance, a strong electromagneticfield is generated around second ground plane 18, thereby irradiatingstrong electromagnetic waves a long way off.

When considering child board 15 that has a memory circuit mountedthereon, child board 15 generally has edges extending over approximately25 to 75 (mm), so that the quarter wavelength resonance occurs atfrequency in a range of approximately 1 to 3 (GHz).

Since conventional data processing circuit 19 internally transmitssignals at a basic frequency around several MHz, its harmonics are alsoon the order of 100 (MHz) at most. Thus, data processing circuit 19 isfree from the quarter wavelength resonance because harmonic componentsare largely lower than the frequency at which the quarter wavelengthresonance occurs in the ground structure.

Recently, however, the trend of increasing the processing speed ofintegrated circuits has increased the basic frequency of data processingcircuit 19 to several hundred MHz, and its harmonics have also spread toas high as several GHz. Since the harmonics overlap the frequency atwhich the aforementioned ground structure is at the quarter wavelength,the ground structure suffers from the resonance.

On the other hand, with the recent development of radio communications,GHz bands are increasingly utilized for radio communications, such asapproximately 1.9 (GHz) in PHS; approximately 800 (MHz), approximately1.5 (GHz), and approximately 2.0 (GHz) in portable telephones; andapproximately 2.4 (GHz) in wireless LAN (Local Area Network) andBluetooth.

From the foregoing background, the resonant frequency associated withthe ground structure overlaps the frequency bands used for radiocommunications, giving rise to a problem that radio communications areimpeded by the ground structure.

While it has been predicted from before that the electromagnetic fieldgenerated by data processing circuit 19 would directly affect radiocommunication unit 12, and countermeasures have been taken therefor,nobody has been able to predict that the operation of data processingcircuit 19 on parent board 11 causes child board 15 and the like to actas a resonant antenna, and an electromagnetic field generated therebyaffects radio communication unit 12.

As illustrated in FIG. 3, in data processing terminal 30 of the thirdprior art example, first and second ground planes 17, 18 are eachshort-circuited by auxiliary connecting means 33 at a corner near anopen edge thereof, so that the ground structure in this prior artexample is free from the quarter wavelength resonance, but can sufferfrom half wavelength resonance. Since the half wavelength resonance isinduced at frequency on the order of 2-6 (GHz) with the aforementionedsize, this range of frequencies, though slightly higher than theprevious examples, will impede the communications as well because it isclose to the frequency bands used for radio communications.

The description made in connection with the aforementioned dataprocessing terminals 10, 20, 30 clarifies that radio communications madeby removably connected radio communication unit 12 are impeded by theground structure within the terminal. Such impeded radio communicationswill be experienced if radio communication unit 12 is disposed near theground structure.

Therefore, communication failures can arise even if a radiocommunication circuit is connected to the data processing terminalthrough a connection cable, or when it is placed near the dataprocessing terminal, though not connected thereto (not shown).

To solve the problem as mentioned above, child board 15 may be coveredwith a metal case (not shown), with the metal case being connected tofirst ground plane 17 of parent substrate 11, to isolate radiocommunication unit 12 from a strong electromagnetic field generated bychild board 15. However, even with the structure using the metal casefor fully covering child board 15, the metal case causes a problem of anincrease in the size of data processing terminal 10, 20, 30.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the problems as mentionedabove, and it is an object of the invention to provide a data processingterminal which reduces the generation of an electromagnetic field thatimpedes radio communications, a parent board and a child board for usein the data processing terminal, a terminal designing apparatus andmethod for use in designing the data processing terminal, a computerprogram for designing the terminal designing apparatus, and aninformation storage device having the computer program stored thereon.

A first data processing terminal according to the present inventioncomprises a first ground plane, a second ground plane, a data processingcircuit, a connector, and resistive connecting means. The first groundplane is comprised of a conductor in a predetermined shape, anddetermines a potential reference. The second ground plane is comprisedof a conductor in a predetermined shape which includes at least aplurality of edges, and is positioned substantially in parallel with thefirst ground plane. The data processing circuit is connected to at leastone of the first ground plane and second ground plane for executing dataprocessing. The connector includes at least a plurality of groundterminals, and connects the second ground plane to the first groundplane at a position near one edge of the second ground plane. Theresistive connecting means is formed to generate a predeterminedresistance value, and connects a position near the other edge of thesecond ground plane opposite to the position of the connector to thefirst ground plane. Consequently, the predetermined resistance valueexists at an open end of a ground structure comprised of the firstground plane, the plurality of ground terminals, and the second groundplane, resulting in reduced Q of the resonance of the ground structure.

In another aspect of the present invention, the ground structurecomprised of the first ground plane, the plurality of ground terminal,and the second ground plane has a characteristic impedance equivalent tothe resistance value of the resistive connecting means, so that the openend of the ground structure is terminated in an impedance matched state.

Also, the resistive connecting means has a resistance value “R” whichsatisfies:[α1×120×π×h/w]≦R<[α2×120×π×h/w](Ω)where “w” represents the length of the edge of the second ground planenear which the resistive connecting means is positioned, “h” representsthe spacing between the first ground plane and the second ground plane,and α1 and α2 are predetermined coefficients which satisfy “α1≦1≦α2, sothat the characteristic impedance of the ground structure is equivalentto the resistance value of the resistive connecting means.

The resistive connecting means has the resistance value “R” whichsatisfies:R=120×π×h/w(Ω)so that the characteristic impedance of the ground structure isidentical to the resistance value of the resistive connecting means.

Alternatively, the resistive connecting means comprises n resistiveconnecting means for connecting the first ground plane to the secondground plane in parallel, and each of the n resistive connecting meanshas a resistance value “R” which satisfies:R=120×π×h/w(Ω)so that the resistance value of the plurality of resistive connectingmeans is identical to the characteristic impedance of the groundstructure, and reduced characteristic impedance exists in series of eachresistive connecting means because there are a plurality of resistiveconnecting means.

Also, one of the resistive connecting means connects a position near thecenter of the edge of the second ground plane to the first ground plane,so that the second ground plane is connected to the first ground planeby the one resistive connecting means in a symmetric state.

Alternatively, two of the resistive connecting means connect positionsnear both ends of the edge of the second ground plane to the firstground plane, respectively, so that the second ground plane is connectedto the first ground plane by the two resistive connecting means in asymmetric state.

Alternatively, three of the resistive connecting means connect positionsnear the center and both ends of the edge of the second ground plane tothe first ground plane, respectively, so that the second ground plane isconnected to the first ground plane by the three resistive connectingmeans in a symmetric state.

Further alternatively, the resistive connecting means is formed in anelongated shape having an overall length equivalent to the edge of thesecond ground plane, and the resistive connecting means is positionedsubstantially in parallel with the edge of the second ground plane, sothat the entire edge of the second ground plane is connected to thefirst ground plane by the single resistive connecting means.

The first ground plane is formed on a parent board which has the dataprocessing circuit mounted thereon, the second ground plane is formed ona child board mounted which has a memory circuit mounted thereon fortemporarily storing data processed by the data processing circuit, theresistive connecting means comprises a resistor mounted on the parentboard and connected to the first ground plane, and the resistor on theparent board is connected to the second ground plane on the child boardthrough a conductor. Since the resistor required for the resistiveconnecting means is mounted on the parent board, the child board has thesame structure as before.

Alternatively, the first ground plane is formed on a parent board whichhas the data processing circuit mounted thereon, the second ground planeis formed on a child board which has a memory circuit mounted thereonfor temporarily storing data processed by the data processing circuit,the resistive connecting means comprises a resistor mounted on the childboard and connected to the second ground plane, and the resistor on thechild board is connected to the first ground plane on the parent boardthrough a conductor. Since the resistor required for the resistiveconnecting means is mounted on the child board, the parent board has thesame structure as before.

Alternatively, the first ground plane is formed on a parent board whichhas the data processing circuit mounted thereon, the second ground planeis formed on a child board which has a memory circuit mounted thereonfor temporarily storing data processed by the data processing circuit,the resistive connecting means comprises two resistors mounted on theparent board and child board, respectively, and connected to the firstground plane and the second ground plane, respectively, and theresistors on the parent board and child board are connected to eachother through a conductor. Since the resistive connecting meanscomprises two resistors, each resistive connecting means has theresistance value reduced to one-half.

Also, a radio communication circuit is removably mounted for makingradio communications with the outside, wherein the radio communicationcircuit is in wired communication with the data processing circuit, sothat even if the radio communication circuit in wired communication withthe data processing circuit makes radio communications, the groundstructure will not generate an electromagnetic field, by the action ofresonance, which impedes the radio communications.

Alternatively, a radio communication circuit is formed integrally withthe data processing terminal for making radio communications with theoutside, wherein the radio communication circuit is in wiredcommunication with the data processing circuit, so that even if radiocommunication circuit in wired communication with the data processingcircuit makes radio communications, the ground structure will notgenerate an electromagnetic field, by the action of resonance, whichimpedes the radio communications.

A terminal designing apparatus according to the present inventioncomprises length input means, length storing means, spacing input means,spacing storing means, and resistance calculating means for use indesigning the data processing terminal of the present invention. In aterminal designing method associated therewith, as the length inputmeans receives the length “w” of a distal edge of the second groundplane opposite to the position of the connector, length storing meansstores the entered length “w”. As the spacing input means receives thespacing “h” between the first ground plane and second ground plane, thespacing storing means stores the entered spacing “h”. Then, theresistance calculating means calculates the resistance value “R” of theresistive connecting means for connecting a position near the distaledge of the second ground plane opposite to the position of theconnector to the first ground plane in accordance with “R=120×π×h/w(Ω)”. Thus, the resistance value is calculated for the resistiveconnecting means which terminates the open end of the ground structurein the data processing terminal in an impedance matched state.

The predetermined shape as referred to in the present invention may beany shape that comprises a plurality of edges and a plurality ofcorners, and contemplates, for example, a rectangular shape which hasfour edges and four corners, and the like. Also, a variety of means asreferred to in the present invention may be formed to implementfunctions associated therewith, and contemplate, for example, dedicatedhardware for performing predetermined functions, a computing deviceprovided with predetermined functions by a computer program,predetermined functions implemented within a computing device by acomputer program, a combination of them, and the like. Also, a varietyof means as referred to in the present invention need not beindividually independent existence, but contemplate a certain meanswhich forms part of another means.

The information storage medium as referred to in the present inventionmay be hardware which has a computer program previously stored thereinfor causing a terminal designing apparatus to execute a variety ofprocessing, and contemplates, for example, ROM (Read Only Memory) and/orHDD (Hard Disc Drive) resident in an apparatus which comprises theterminal designing apparatus, CD (Compact Disc)-ROM and/or FD (FloppyDisc) exchangeably loaded into the apparatus which comprises theterminal designing apparatus, and the like.

Also, the terminal designing apparatus as referred to in the presentinvention may be any hardware that can read a computer program toexecute corresponding processing operations, and contemplates, forexample, hardware which is mainly based on a CPU (Central ProcessingUnit) connected to a variety of devices such as ROM, RAM, I/F(Interface) unit, and the like.

In the present invention, causing the terminal designing apparatus toexecute a variety of operations in accordance with a computer programalso contemplates causing the terminal designing apparatus to controlthe operation of various devices. For example, storage of a variety ofdata in the terminal designing apparatus contemplates storing a varietyof data in an information storage medium such as RAM which is containedin the terminal designing apparatus as its part, storing a variety ofdata in an information storage medium such as FD which is exchangeablyloaded into the terminal designing apparatus, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating the internal structure of afirst exemplary conventional data processing terminal;

FIG. 2 is a perspective view illustrating the internal structure of asecond exemplary conventional data processing terminal;

FIG. 3 is a perspective view illustrating the internal structure of athird exemplary conventional data processing terminal;

FIG. 4 is a schematic diagram illustrating electric features such as afirst ground plane, a second ground plane, and the like in the firstexemplary conventional data processing terminal;

FIG. 5A is a schematic diagram illustrating the structure of an invertedL-shaped antenna;

FIG. 5B is a schematic diagram illustrating the structure of an invertedF-shaped antenna;

FIG. 6 is a perspective view illustrating the internal structure of adata processing terminal according to a first embodiment of the presentinvention;

FIG. 7 is a schematic diagram illustrating electric features such as afirst ground plane, a second ground plane and, the like;

FIG. 8 is a block diagram illustrating the physical structure of aterminal designing apparatus according to the first embodiment of thepresent invention;

FIG. 9 is a schematic diagram illustrating the logical structure of theterminal designing apparatus;

FIG. 10 is a flow chart illustrating a terminal designing methodassociated with the terminal designing apparatus;

FIG. 11 is a perspective view illustrating the internal structure of afirst exemplary modification to the data processing terminal;

FIG. 12 is a perspective view illustrating the internal structure of asecond exemplary modification to the data processing terminal;

FIG. 13 is a perspective view illustrating the internal structure of athird exemplary modification to the data processing terminal;

FIG. 14A is a top plan view illustrating a main portion of a fourthexemplary modification to the data processing terminal;

FIG. 14B is a top plan view illustrating a main portion of a fifthexemplary modification to the data processing terminal;

FIG. 15A is a top plan view illustrating a main portion of a sixthexemplary modification to the data processing terminal;

FIG. 15B is a top plan view illustrating a main portion of a seventhexemplary modification to the data processing terminal;

FIG. 16 is a top plan view illustrating a main portion of an eighthexemplary modification to the data processing terminal;

FIG. 17 is a perspective view illustrating the internal structure of adata processing terminal according to a second embodiment of the presentinvention;

FIG. 18 is a bottom view illustrating a main portion of a child board;

FIG. 19A is a schematic diagram illustrating an electromagneticsimulation model;

FIG. 19B is a schematic diagram illustrating an electromagneticsimulation model; and

FIG. 20 is a characteristic diagram showing the frequency characteristicof distant radiation electric field strength.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention will hereinafter bedescribed with reference to FIGS. 6 to 10. However, parts in thefollowing embodiments identical to those in the aforementioned prior artexamples are designated the same names and reference numerals, anddetailed description thereon will be omitted.

First, as illustrated in FIGS. 6 and 7, data processing terminal 40according to the first embodiment comprises a variety of data processingcircuits 19 mounted on large rectangular parent board 11 in a mannersimilar to data processing terminals 10, 20, 30 previously described asthe first to the third prior art examples. Radio communication unit 12,which is in wired communication with data processing circuit 19,communicates with the outside over the air in a frequency band near 1.9(GHz).

Parent board 11 comprises smaller rectangular child board 15 removablymounted thereon by connector 14, and second ground plane 18 of childboard 15 is connected to first ground plane 17 of parent board 11through connector 14.

First ground plane 17 and second ground plane 18 thus electrically andmechanically connected through connector 14 and placed in parallel witheach other are further electrically connected through resistiveconnecting means 41. In resistive connecting means 41, connection pads31, 32 of parent board 11/child boards 15, which are electricallycontinuous to first ground plane 17/second ground plane 18, are inelectrical communication through tubular metal columns and screws (notshown) made, for example, of a resistive material.

Also, in data processing terminal 40 of this embodiment, thoughconnector 14 is positioned near one longer side of rectangular childboard 15 in parallel therewith, it differs from the aforementioned dataprocessing terminal 30 and the like in that point-like resistiveconnecting means 41 is positioned near the center of the other longerside of child board 15.

Then, in data processing terminal 40 of this embodiment, resistancevalue “R” of resistive connecting means 41 satisfies “R=120×π×h/w (Ω)”,where “w” represents the length of an edge of second ground plane 18near which resistive connecting means 41 is positioned, and “h”represents the spacing between first ground plane 17 and second groundplane 18.

Consequently, in data processing terminal 40 of this embodiment, theground structure comprised of first ground plane 17, a plurality ofground terminals, and second ground plane 18 has a characteristicimpedance identical to the resistance value of resistive connectingmeans 41, thus achieving impedance matching at an open end of theterminated ground structure.

In data processing terminal 40 of this embodiment, when one end ofconnector 14 is positioned near a corner of second ground plane 18 asmentioned above, this position is approximated to the corner of secondground plane 18, and when resistive connecting means 41 is positionednear an edge of second ground plane 18, this position is approximated tothe edge of second ground plane 18.

With the configuration as described above, in data processing terminal40 of this embodiment, data processing circuit 19 on parent board 11executes data processing to generate an electromagnetic field when radiocommunication unit 12 makes a radio communication, so that theelectromagnetic field acts on the ground structure which has first andsecond ground planes 17, 18 connected through ground terminals ofconnector 14.

However, second ground plane 18 is connected to first ground plane 17through resistive connecting means 41 at the center of an edge thereofwhich is an open end of the ground structure, and resistive connectingmeans 41 has a resistance value identical to the characteristicimpedance of the ground structure.

Thus, the ground structure has the open end terminated in an impedancematched state, so that even if the electromagnetic field of dataprocessing circuit 19 acts on the ground structure, this will not leadto the generation of a strong electromagnetic field, by the action ofresonance, which would impede radio communications. Consequently, dataprocessing terminal 40 of this embodiment can prevent impeded radiocommunications of radio communication unit 12 to satisfactorily carryout radio communications.

Moreover, in data processing terminal 40 of this embodiment, connector14 is identical in position and structure to the prior art with theaddition of single extra resistive connecting means 41, so that it isalso simple in structure and easy to assemble. Further, since resistiveconnecting means 41 is positioned near the center of the distal longerside of child board 15 from connector 14, second ground plane 18 can besatisfactorily connected to first ground plane 17 in a symmetric stateif resistive connecting means 41 mechanically holds child board 15 aswell.

Now, the following description will be made on terminal designingapparatus 50 in this embodiment which is utilized for designing dataprocessing terminal 40 in the structure as described above. Asillustrated in FIG. 8, terminal designing apparatus 50 of thisembodiment comprises CPU 51 which serves as main hardware of a computer.CPU 51 is connected through bus line 52 to hardware such as ROM 53; RAM54; HDD 55; FDD (FD Drive) 57 which is exchangeably loaded with FD 56;CD drive 59 which is exchangeably loaded with CD-ROM 58; keyboard 60;mouse 61; display 62; I/F unit 63, and the like.

In terminal designing apparatus 50 of this embodiment, hardware such asROM 53, RAM 54, HDD 55, exchangeable FD 56, exchangeable CD-ROM 58, andthe like corresponds to information storage media, and computer programsfor CPU 51 and a variety of data are stored in at least one of them assoftware.

For example, a computer program which causes CPU 51 to execute a varietyof processing operations has been previously stored on FD 56 or CD-ROM58. Such software has been previously installed in HDD 55, and is copiedto RAM 54 upon start of terminal designing apparatus 50, and read by CPU51.

As CPU 51 reads a proper computer program to execute a variety ofprocessing operations, terminal designing apparatus 50 of thisembodiment logically comprises a variety of means such as length inputmeans 71, length storing means 72, spacing input means 73, spacingstoring means 74, resistance calculating means 75, and the like, asillustrated in FIG. 9.

Each of input means 71, 73 corresponds to a function of CPU 51 forrecognizing data entered through keyboard 60 in accordance with acomputer program stored in RAM 54, while each of storing means 72, 74corresponds to a storage area or the like reserved in HDD 55 in orderfor CPU 51 to recognize data in accordance with the computer program.

Length input means 71 receives length “w” of the other edge of secondground plane 18 opposing the position of connector 14, and lengthstoring means 72 stores length “w” entered into length input means 71.Spacing input means 73 receives spacing “h” between first ground plane17 and second ground plane 18, and spacing storing means 74 storesspacing “h” entered into spacing input means 73.

Then, resistance calculating means 75, which corresponds to a functionof CPU 51 for executing predetermined data processing and the like inaccordance with a computer program, calculates resistance value “R” ofresistive connecting means 41 as “R=120×π×h/w (Ω)” based on the datastored in respective storing means 72, 74.

While a variety of means as mentioned above are implemented as requiredby hardware such as keyboard 60, display 62, and the like, theirnucleuses are implemented by CPU 51, hardware of terminal designingapparatus 50, which functions in accordance with software stored in aninformation storage medium such as RAM 54 and the like.

Such software is stored in an information storage medius such as RAM 54or the like as a computer program for causing CPU 51 and the like toexecute such processing operations as length input processing forreceiving length “w” entered through keyboard 60 or the like; lengthstorage processing for storing the entered length “w” in HDD 55 or thelike; spacing input processing for receiving entered spacing “h”;spacing storage processing for storing entered spacing “h”; resistancecalculation processing for calculating resistance value “R” of resistiveconnecting means 41 as “R=120×π×h/w (Ω)”; and the like.

In data processing terminal 40 of this embodiment configured asdescribed above, radio communication unit 12 in wired communication withdata processing circuit 19 can communicate with the outside over theair. In this event, a high frequency electromagnetic field generated bydata processing circuit 19 acts on the ground structure comprised offirst ground plane 17, connector 14, and second ground plan 18.

However, in data processing terminal 40 of this embodiment, secondground plane 18 has an edge, distal from connector 14, connected tofirst ground plane 17 through resistive connecting means 41, andresistive connecting means 41 has a resistance value which matches withthe characteristic impedance of the ground structure.

Thus, the ground structure has an open end terminated in impedancematched state, and therefore will not resonate with the acting highfrequency electromagnetic field from data processing circuit 19 togenerate a strong electromagnetic field which would impede radiocommunications of radio communication unit 12. Consequently, in dataprocessing terminal 40 of this embodiment, radio communication unit 12can satisfactorily carry out radio communications.

Now, the following description will be made on a terminal designingmethod associated with terminal designing apparatus 50 for use indesigning such data processing terminal 40. Terminal designing apparatus50 of this embodiment can calculate the resistance value of resistiveconnecting means 41 in data processing terminal for which length “w” ofsecond ground plane 18, and spacing “h” between first ground plane 17and second ground plane 18 have been determined.

In this event, as illustrated in FIG. 10, terminal designing apparatus50 displays on display 62 a guidance text such as “enter the followingdata” together with items to be entered such as “length w=(mm), spacingh=(mm)” (step S3).

Thus, as an operator (not shown) who designs data processing terminal 40enters desired numerical data for the aforementioned items to be enteredthrough keyboard 60 or the like (step S4), terminal designing apparatus50 stores the entered numerical data (step S5).

The numerical data thus entered are displayed at respective positions ofthe items to be entered. When numerical data have been previouslyentered and remain stored (step S1), the numerical data are displayed atthe positions of associated items to be entered as changeable defaultvalues (steps S2, S3).

Then, as terminal designing apparatus 50 of this embodiment receives aninstruction to start the processing after both of length “w” and spacing“h” have been stored in the associated storing means (steps S6, S7),terminal designing apparatus 50 calculates resistance value “R” ofresistive connecting means 41 as “R=120×π×h/w (Ω)” based on the storeddata (step S8).

Since resistance value “R” of resistive connecting means 41 thuscalculated is displayed on display 62 (step S9), the operator canconnect first and second ground planes 17, 18 of data processingterminal 40 to be manufactured with resistive connecting means 41 havingresistance value “R”.

It should be noted that the present invention is not limited to theforegoing embodiment, but contemplates a variety of modificationswithout departing from the gist thereof. For example, while theforegoing embodiment has illustrated that terminal designing apparatus50 provides resistance value “R” in response to length “w” and spacing“h” entered thereinto, terminal designing apparatus 50 may declarewhether or not “R=120×π×h/w (Ω)” is established in response to length“w” and spacing “h” entered thereinto.

Also, terminal designing apparatus 50 in the foregoing embodiment hasillustrated that a variety of means are logically implemented as avariety of functions of terminal designing apparatus 50 by CPU 51 whichoperates in accordance with computer programs stored in RAM 54 and thelike. However, each of a variety of such means can be formed asdedicated hardware, or some can be stored in RAM 54 and the like assoftware while some is formed as hardware.

Further, while the foregoing embodiment has illustrated that resistancevalue “R” of resistive connecting means 41 in data processing terminal40 satisfies “R=120×π×h/w (Ω)”, predetermined coefficient α1, α2 whichsatisfy “α1≦1≦α2”, for example, may be used to provide resistance value“R” of resistive connecting means 41 which falls under the followingrange:[α1×120×π×h/w]≦R<[α2×120×π×h/w]

Even in this event, since the characteristic impedance of the groundstructure in data processing terminal 40 is equivalent, not completelyidentical, to the resistance value of resistive connecting means 41, itis possible to prevent the generation of a strong electromagnetic fieldwhich impedes radio communications. Even if the resistance value ofresistive connecting means 41 is not equivalent to the characteristicimpedance of the ground structure in data processing terminal 40, apredetermined resistance value can contribute to a reduction in Q ofresonance of the ground structure, so that a resulting electromagneticfield can be reduced.

Also, while the foregoing embodiment has illustrated that radiocommunication unit 12 is removably mounted in data processing terminal40, radio communication unit 12 can be integrally secured thereon, radiocommunication unit 12 can be connected through a connection cable (notshown), or separate radio communication unit 12 can be used in theneighborhood without being connected thereto, by way of example.

Likewise, while the foregoing embodiment has illustrated that childboard 15 is removably mounted on parent board 11, this can be integrallysecured thereon. Also, while the foregoing embodiment has illustratedthat child board 15 and radio communication unit 12 are disposed on thesame side of parent board 11, child board 15 can be positioned on thefrond side of parent board 11, while radio communication unit 12 can bepositioned on the back side of parent board 11, by way of example.

Further, while data processing terminal 40 in the foregoing embodimenthas illustrated that data processing circuit 19 is mounted on parentboard 11 to which child board 15 is connected, data processing circuit19 can be mounted only on child board 15, or can be distributivelymounted on both parent board 11 and child board 15.

When data processing circuit 19 is mounted only on child board 15 asmentioned above, parent board 11 is not needed as a circuit board, sothat first ground plane 17, which has a large area and a large capacity,is preferably formed as a dedicated ground member separate from thecircuit board.

Also, while the foregoing embodiment has illustrated that dataprocessing terminal 40 is formed for portable applications, this canalso be formed for stationary applications. Also, while the foregoingembodiment has illustrated that the communication frequency of radiocommunication unit 12 is near 1.9 (GHz) for PHS, this can be near 800(MHz), 1.5 (GHz), or 2.0 (GHz) for portable telephones, or can be near2.4 (GHz) for Bluetooth as well.

Further, while the data processing terminal 40 of the foregoingembodiment has illustrated that single point-shaped resistive connectingmeans 41 is positioned near the center of the edge of child board 15distal from connector 14, a plurality of such resistive connecting means41, for example, may be provided.

For example, in data processing terminal 80 illustrated in FIG. 11 as afirst exemplary modification to the foregoing embodiment, two resistiveconnecting means 81 are positioned one by one at corners of rectangularchild board 15 at both ends of one side thereof, and in data processingterminal 82 illustrated in FIG. 12 as a second exemplary modification,three resistive connecting means 83 are positioned, each at corners ofrectangular child board 15 at both ends and the center of one sidethereof.

In these modifications, since total resistance value “R” of a pluralityof resistive connecting means 81 or 83 also satisfies “R=120×π×h/w (Ω)”,resistance value “Rn” of each of two resistive connecting means 81satisfies “Rn=240×π×h/w (Ω)”, while resistance value “Rn” of each ofthree resistive connecting means 83 satisfies “Rn=360×π×h/w (Ω)”.

In this way, as first and second ground planes 17, 18 are connected inparallel with each other through a plurality of resistive connectingmeans 81, 83, parasitic inductance existing in series with resistiveconnecting means 81, 83 is reduced so that the ground structure can beterminated in a impedance matched state over a wide band, thereby makingit possible to prevent the generation of a strong electromagnetic field,which impedes radio communications, over a wide band.

Further, in data processing terminal 84 illustrated in FIG. 13 as athird exemplary modification, resistive connecting means 85 comprises anelongated metal member which has the overall length equivalent to oneside of child board 15, and this single resistive connecting means 85 isdisposed in parallel with one side of child board 15. As one overallside of second ground plane 18 is connected to first ground plane 17through elongated resistive connecting means 85, it is possible tominimize parasitic inductance existing in series with resistiveconnecting means 85.

Also, while the foregoing embodiment has illustrated that childsubstrate 15 and second ground plane 18 are formed in simple rectangularshape, second ground plane 90 may be formed in L-shape, as illustratedin FIG. 14A as a fourth exemplary modification, or second ground plane91 may be formed in T-shape, as illustrated in FIG. 14B as a fifthexemplary modification.

Even in such modifications, resistive connecting means 92, 93 may bepositioned near an edge of second ground plane 90, 91 in differentshape, distal from connector 14, such that the resistance value thereofsatisfies “R=120×π×h/w (Ω)” for length “w” of the edge.

However, if second ground planes 90, 91 are formed in L-shape andT-shape as mentioned above, there is a concern that the portionextending outward on a lateral side(s) in the figure can act as an openend(s). Therefore, if this can causae a problem, resistive connectingmeans 94, 95 are preferably disposed in the laterally extendingportions, as illustrated in FIGS. 15A and 15B as a sixth and a seventhexemplary modification.

Even in such configurations, however, resistive connecting means 92-95are only required to satisfy the resistance value calculated by“R=120×π×h/w (Ω)” for lengths “w” of the respective edges near whichthey are disposed. Therefore, for example, when resistive connectingmeans 92, 94 are disposed near the edges having different lengths “w1,w2” in L-shaped second ground plane 90, resistive connecting means 92,94 also have different resistance values as calculated by “R1=120×π×h/w1(Ω)” and “R2=120×π×h/w2 (Ω)”, respectively. This also applies toT-shaped second ground plane 91.

Further, while data processing terminal 40 and the like in the foregoingembodiment have illustrated that connector 14 is disposed along an edgeof second ground plane 18, connector 14 can be disposed in a centralportion of second ground plane 96, as illustrated in FIG. 16.

In this modification, since this structure is equivalent to a structurewhich comprises a pair of an integrally joined second ground planes 18,each having connector 14 disposed along one edge, two resistiveconnecting means 41 are preferably disposed one by one near each ofedges of second ground planes 96 positioned on both sides of connector14.

Also, while data processing terminal 40 and the like in the foregoingembodiment have illustrated that the connector is comprised of a pair ofvertically removable connectors 14, the connector can be comprised ofconnector 21 to which one edge of child board 15 is mounted and removedin the transverse direction, as is the case with data processingterminal 20 illustrated in FIG. 2.

Further, in data processing terminals 40, 80, 82 in the foregoingembodiments, each of resistive connecting means 41, 81, 83 is presumablycomprised of a tubular metal column and a screw, while in dataprocessing terminal 84, resistive connecting means 85 is illustrativelycomprised of an elongated metal member. However, it is not easy torealize a predetermined resistance value with resistive connecting means41 and the like in such structures.

Now, data processing terminal 100 which solves the foregoing problemswill be described below with reference to FIGS. 17 and 18 as a secondembodiment of the present invention. First, as illustrated in FIG. 17,data processing terminal 100 of this embodiment has connection pad 101formed on the top surface of parent board 11, wherein this connectionpad 101 is electrically continuous to first ground plane 17.

Connection pad 102 is also formed on the bottom surface of childsubstrate 15, and is electrically continuous to connection pad 101 ofparent substrate 11 through conductive metal column 34 and screw 35.However, as illustrated in FIG. 18, resistor 103, which is resistiveconnecting means, is mounted on the bottom surface of child board 15,such that connection pad 102 of child board 15 is electricallycontinuous to second ground plane 18 through resistor 103.

More specifically, a pair of mounting pads 104, 105 are formed on thebottom surface of child board 15, and one mounting pad 104 is formedintegrally with connection pad 102. The other mounting pad 105 iselectrically continuous to second ground plane 18 through viahole 106,and resistor 103 has both ends connected to the pair of mounting pads104, 105.

In such a configuration, in data processing terminal 100 of thisembodiment, resistor 103, which is the resistive connecting means, ismounted only on child board 15, so that parent board 11 may be in thesame structure as before. For this reason, when data processing terminal100 which is mounted only with parent board 11 but not with child board15 is sold as a product such that a customer adds optional child board15 to data processing terminal 10 as desired, resistor 103 may bemounted only on child board 15 for preventing the problem caused by theaddition.

Therefore, useless measures need not be taken to initial data processingterminal 100 which does not contain child board 15, thus making itpossible to improve the productivity through simplification of thestructure of data processing terminal 100 in the initial state. Also,even when child board 15 is initially mounted in data processingterminal 100, data processing terminals 100 are produced in volume witha high productivity because no modification is required in the design ofparent board 15 when child board 15 is changed in size and shape.

It should be noted that the present invention is not either limited tothe foregoing embodiment, but contemplates a variety of modificationswithout departing from the gist thereof. For example, while theforegoing embodiment has illustrated that resistor 103, which serves asthe resistive connecting means, is mounted only on child board 15,resistor 13 may be mounted only on parent board 11.

In this case, child board 15 may be in the same structure as before, sothat even if a plurality of types of child boards 15, for example, aremade exchangeable, resistor 103 need not be mounted on each of them,thus improving the productivity of the plurality of types of childboards 15. Alternatively, two resistors can be mounted one on parentboard 11 and one on child board 15, in which case each of the resistorscan have one half of the resistance value.

Now, the result of experiments made by the inventors will be describedbelow with reference to FIGS. 19A, 19B and 20.

The inventors installed an existing software application for anelectromagnetic simulation based on an FDTD (Finite Differential TimeDomain) method into a general personal computer to calculate thefrequency characteristics of distant radiation electric field strengthsof the aforementioned data processing terminals 10, 30, 40, 82. It canbe readily supposed that though the distant radiation electric fieldstrength is not the same as electromagnetic interference due to anelectromagnetic field near a terminal, a higher distant radiationelectric field strength causes higher susceptibility to theelectromagnetic interference in the neighborhood.

FIGS. 19A and 19B illustrate an electromagnetic field simulation model.First ground plane 17 was modeled by a complete conductor having a widthdimension of 160 (mm), a length dimension of 70 (mm), and an infinitelysmall thickness, while second ground plane 18 was modeled by a completeconductor having a width dimension of 40 (mm), a length dimension of 50(mm), and an infinitely small thickness. Further, connector 14 wasmodeled by a complete conductor having a width dimension of 20 (mm), aninfinitely small length dimension, and a thickness of 4 (mm), and wasdisposed along one longer side of second ground plane 18.

Data processing circuit 19 was composed of a signal wire, a resistor,and a voltage source. The signal wire was modeled by a rod-shapedcomplete conductor having infinitely small width and thicknessdimensions and a length dimension of 5 (mm), and disposed at height of 2(mm) from first ground plane 17. A 1-ohm resistor was inserted betweenone end of the signal wire and first ground plane 17, while a rod-likecomplete conductor was inserted between the other end of the signal wireand first ground plane 17. The voltage source was disposed at the centerof the signal wire in parallel with first ground plane 17. The voltagesource was chosen to have an internal impedance of 0 (Ω) and an outputvoltage of 1 (V).

Data processing circuit 19 was positioned on ground plane 17 beneathsecond ground plane 18 near the center thereof with its longitudinaldirection orthogonal to connector 14. While data processing circuit 19should essentially be mounted across the entirety of parent board 11,the foregoing model was created for showing that even a signal wire ofas short as 5.0 (mm) would cause second ground plane 18 to resonate.

This simulation was performed to investigate two each of data processingterminals according to the prior art examples and the present invention.Prior Art Example 1 corresponds to data processing terminal 10 in whichan open end is formed on the opposing edge distal from connector 14which connects first ground plane 17 to second ground plane 18, andPrior Art Example 2 corresponds to data processing terminal 30 whichhave two ground planes 17, 18 connected through a complete conductor atA-point and D-point which are situated at diagonal positions of secondground plane 2.

Present Invention 1 corresponds to data processing terminal 40 which hastwo ground planes 17, 18 connected through resistive connecting means 41at the center B of an edge, and Present invention 2 corresponds to dataprocessing terminal 82 which has two ground planes 17, 18 connectedthrough resistive connecting means 83 at three points A, B, C along anedge.

Since spacing h between two ground planes 17, 18 is 4 (mm), and length wof the edge of second ground plane 18 distal from connector 16 is 40(mm), resistance value R of the resistive connecting means is calculatedto be 37.7 (Ω) from the equation “R=120×π×h/w (Ω)”. Thus, in PresentInvention 1, the resistance value of resistive connecting means 41 waschosen to be 37.7 (Ω), while in Present Invention 2, resistance value ofresistive connecting means 83 was chosen to be 113 (Ω) which is thevalue three times as large as R.

The FDTD-based electromagnetic field simulation prepares a calculationregion including a calculation model, and defines an absorption boundaryregion around the calculation region. Further, the calculation region isdivided by a mesh. In this calculation, the prepared calculation regionhad a width dimension of 260 (mm), a length dimension of 170 (mm), and aheight dimension of 100 (mm), and a calculation model was disposed atthe center of the region. A 10-layer PML (Perfectly Matched Layer)absorption boundary condition was used for the absorption boundarycondition. Further, the calculation region was divided by a uniform meshat intervals of 5.0 (mm) in the horizontal and vertical directions and2.0 (mm) in the thickness direction.

Under the foregoing conditions, the distant radiation electric fieldstrength was calculated in a range of 1.0-3.0 (GHz). FIG. 20 shows theresult of the calculation. The origin was defined at the center of firstground plane 17, and maximum distant radiation electric field strengthvalues were plotted on an XY-plane, a YX-plane, and a ZX-plane. In thecalculation model for Prior Art Example 1, the result was normalizedbased on the maximum distant radiation electric field strength whensecond ground plane 17 and connector 14 were removed.

In data processing terminal 10 of Prior Art Example 1, there is a peaknear 1.4 (GHz). The distance from the position of connector 14 on secondground plane 18 to the other edge thereof is 45 (mm), and this lengthconverts into the quarter wavelength at frequency of 1.7 (GHz). Assumingthat the resonant frequency is more or less lower because of secondground plane 18 being in the shape of a wide conductor plate, it can besupposed that the peak is caused by the resonance of the groundstructure which is formed of first ground plane 17, second ground plane18, and connector 14 which connects both ground planes 17, 18.

In data processing terminal 20 of Prior Art Example 2, there is a peaknear 2.2 (GHz). The distance from the position of connector 14 on secondground plane 18 to the other edge thereof converts into a halfwavelength at frequency of 3.4 (GHz) which is largely different from theaforementioned peak frequency. However, assuming that the resonantfrequency is more or less lower because of the asymmetrically positionedA-point at which both ground planes 17, 18 are short-circuited, andbecause of second ground plane 18 being in the shape of a wide conductorplate, as is the case with the foregoing, it can be supposed that thispeak is also caused by the resonance of the ground structure which isformed of first ground plane 17, second ground plane 18, connector 14,and auxiliary connecting means 33 at A- and D-points.

While data processing terminal 30 of Prior Art Example 2 can increasethe resonant frequency as compared with data processing terminal 10 ofPrior Art Example 1, a strong electromagnetic field is still generatedin frequency bands utilized for radio communications. For example, sincePHS utilizes approximately 1.9 (GHz); portable telephones, about 2.0(GHz); and wireless LAN and bluetooth, approximately 2.4 (GHz), dataprocessing terminal 30 of Prior Art 2 is susceptible to impediments tothese radio communications.

On the other hand, in data processing terminals 40, 82 of PresentInvention 1, 2, the distant radiation electric field strength does notpresent a peak over a wide band of at least 1.0 to 3.0 (GHz), and thisis equivalent to the absence of second ground plane 18 and connector 14which are defined as the references. In addition, an increase in levelwith respect to the references is 2.0 (dB), which is very low ascompared with Prior Art Examples 1, 2.

In the ground structure comprised of first ground plane 17, secondground plane 18, and connector 14, strong resonance caused by the groundstructure can be limited over a wide band by adding a resistor having aresistance value identical to the characteristic impedance value of atransmission line formed of first and second ground planes 17, 18 to anedge of second ground plane 18 distal from connector 14.

As described above, the present invention provides the followingadvantages.

In a first data processing terminal according to the present invention,the resistive connecting means which generates a predeterminedresistance value connects a position near the distal edge of the secondground plane opposite to the position of the connector to the firstground plane, so that the resistive connecting means can reduce Q of theresonance of the ground structure comprised of the first ground plane,the plurality of ground terminals, and the second ground plane, therebymaking it possible to reduce the resonance of the ground structurecaused by an electromagnetic field of the data processing circuit toprevent the generation of a strong electromagnetic field which impedesradio communications.

In another aspect of the present invention, the ground structurecomprised of the first ground plane, the plurality of ground terminal,and the second ground plane has a characteristic impedance equivalent tothe resistance value of the resistive connecting means, so that theground structure can have the open end terminated in an impedancematched state, thereby preventing the resonance of the ground structurecaused by an electromagnetic field of the data processing circuit toprevent without fail the generation of a strong electromagnetic fieldwhich impedes radio communications.

Also, the resistive connecting means has the resistance value “R” whichsatisfies:[α1×120×π×h/w]≦R<[α2×120×π×h/w](Ω)where “w” represents the length of the edge of the second ground planenear which the resistive connecting means is positioned, “h” representsthe spacing between the first ground plane and the second ground plane,and α1 and α2 are predetermined coefficients which satisfy “α1≦1≦α2, sothat the characteristic impedance of the ground structure can be madeequivalent to the resistance value of the resistive connecting means.

Alternatively, the resistive connecting means has the resistance value“R” which satisfies:R=120×π×h/w(Ω)so that the characteristic impedance of the ground structure can be madeidentical to the resistance value of the resistive connecting means.

Alternatively, the resistive connecting means comprises n resistiveconnecting means for connecting the first ground plane to the secondground plane in parallel, and each of the n resistive connecting meanshas a resistance value “R” which satisfies:R=120×π×h/w(Ω)so that the resistance value of the plurality of resistive connectingmeans can be made identical to the characteristic impedance of theground structure, and the characteristic impedance existing in series ofeach resistive connecting means can be reduced because there are aplurality of resistive connecting means, thus terminating the groundstructure in an impedance matched state over a wide band.

Also, when one of the resistive connecting means connects a positionnear the center of the edge of the second ground plane to the firstground plane; or

when two of the resistive connecting means connect positions near bothends of the edge of the second ground plane to the first ground plane,respectively; or

when three of the resistive connecting means connect positions near thecenter and both ends of the edge of the second ground plane to the firstground plane, respectively,

the second ground plane can be connected to the first ground plane by apredetermined number of resistive connecting means in a symmetric state.

Alternatively, the resistive connecting means is formed in an elongatedshape having an overall length equivalent to the edge of the secondground plane, and is positioned substantially in parallel with the edgeof the second ground plane, so that the entire edge of the second groundplane can be connected to the first ground plane by the single resistiveconnecting means.

The resistive connecting means comprises a resistor which is mounted onthe parent board and connected to the first ground plane, and theresistor on the parent board is connected to the second ground plane onthe child board through a conductor. Since the resistor required for theresistive connecting means is mounted on the parent board, the childboard can be in the same structure as before.

Alternatively, the resistive connecting means comprises a resistor whichis mounted on the child board and connected to the second ground plane,and the resistor on the child board is connected to the first groundboard on the parent board through a conductor. Since the resistorrequired for the resistive connecting means is mounted on the childboard, the parent board can be in the same structure as before.

Alternatively, the resistive connecting means comprises two resistorsmounted on the parent board and child board, respectively, and connectedto the first ground plane and second ground plane, respectively, and theresistors on the parent board and child board are connected to eachother through a conductor. Since the resistive connecting meanscomprises two resistors, each resistive connecting means can have theresistance value reduced to one-half.

Also, a radio communication circuit is removably mounted for makingradio communications with the outside, wherein the radio communicationcircuit is in wired communication with the data processing circuit; or

a radio communication circuit is formed integrally with the dataprocessing terminal for making radio communications with the outside,wherein the radio communication circuit is in wired communication withthe data processing circuit,

so that the ground structure will not generate an electromagnetic field,by the action of resonance, which impedes the radio communications ofthe radio communication circuit, thus permitting the radio communicationcircuit to satisfactorily make radio communications.

In a terminal designing method associated with a terminal designingapparatus, resistance calculating means calculates the resistance value“R” of the resistive connecting means for connecting a position near thedistal edge of the second ground plane opposite to the position of theconnector to the first ground plane in accordance with “R=120×π×h/w(Ω)”. Thus, the resistance value can be calculated for the resistiveconnecting means which terminates the open end of the ground structurein the data processing terminal in an impedance matched state.

1. A data processing terminal comprising: a first ground plane comprisedof a conductor in a predetermined shape for determining a potentialreference; a second ground plane comprised of a conductor in apredetermined shape having at least a plurality of edges, and positionedsubstantially in parallel with said first ground plane; a dataprocessing circuit connected to at least one of said first ground planeand said second ground plane; a connector for connecting a position nearone edge of said second ground plane to said first ground plane througha plurality of ground terminals; and resistive connecting means forconnecting a position near another edge of said second ground planeopposite to the position of said ground connector to said first groundplane with a predetermined resistance value, wherein, said first groundplane, said plurality of said ground terminals, and said second groundplane make up a ground structure, said ground structure having acharacteristic impedance equivalent to the resistance value of saidresistive connecting means, and said resistive connecting means has aresistance value “R” which satisfies:[α1×120×π×h/w]≦R<[α2×120×π×h/w](Ω) where “w” represents a length of anedge of said second ground plane near which said resistive connectingmeans is positioned, “h” represents a spacing between said first groundplane and said second ground plane, and α1 and α2 are predeterminedcoefficients which satisfy “α1≦1<α2.
 2. The data processing terminalaccording to claim 1, wherein: said resistive connecting means has theresistance value “R” which satisfies:R=120×π×h/w(Ω).
 3. The data processing terminal according to claim 2,wherein: said resistive connecting means comprises n resistiveconnecting means for connecting said first ground plane to said secondground plane in parallel; and each of said n resistive connecting meanshas a resistance value “R” which satisfies:R=120×π×h/w(Ω).
 4. The data processing terminal according to claim 2,wherein one of said resistive connecting means connects a position neara center of an edge of said second ground plane to said first groundplane.
 5. The data processing terminal according to claim 2, wherein twoof said resistive connecting means connect positions near both ends ofan edge of said second ground plane to said first ground plane,respectively.
 6. The data processing terminal according to claim 2,wherein three of said resistive connecting means connect positions neara center and both ends of an edge of said second ground plane to saidfirst ground plane, respectively.
 7. The data processing terminalaccording to claim 2, wherein: said first ground plane is formed on aparent board which has said data processing circuit mounted thereon;said second ground plane is formed on a child board which has a memorycircuit mounted thereon for temporarily storing data processed by saiddata processing circuit; said resistive connecting means comprises aresistor mounted on said parent board and connected to said first groundplane; and said resistor on said parent board is connected to saidsecond ground plane on said child board through a conductor.
 8. The dataprocessing terminal according to claim 2, wherein: said first groundplane is formed on a parent board which has said data processing circuitmounted thereon; said second ground plane is formed on a child boardwhich has a memory circuit mounted thereon for temporarily storing dataprocessed by said data processing circuit; said resistive connectingmeans comprises a resistor mounted on said child board and connected tosaid second ground plane; and said resistor on said child board isconnected to said first ground plane on said parent board through aconductor.
 9. The data processing terminal according to claim 2,wherein: said first ground plane is formed on a parent board which hassaid data processing circuit mounted thereon; said second ground planeis formed on a child board which has a memory circuit mounted thereonfor temporarily storing data processed by said data processing circuit;said resistive connecting means comprises two resistors, one of saidresistors being mounted on said parent board and connected to said firstground plane, and the other of said resistors being mounted on saidchild board and connected to said second ground plane; and saidresistors on said parent board and said child board are connected toeach other through a conductor.
 10. The data processing terminalaccording to claim 2, further comprising a radio communication circuitremovably mounted therein for making radio communications with theoutside; wherein said radio communication circuit is in wiredcommunication with said data processing circuit.
 11. The data processingterminal according to claim 2, further comprising: a radio communicationcircuit formed integrally therewith for making radio communications withthe outside; wherein said radio communication circuit is in wiredcommunication with said data processing circuit.
 12. The data processingterminal according to claim 4, wherein: said resistive connecting meansis formed in an elongated shape having an overall length equivalent toan edge of said second ground plane; and said resistive connecting meansis positioned substantially in parallel with the edge of said secondground plane.
 13. The data processing terminal according to claim 3,wherein two of said resistive connecting means connect positions nearboth ends of an edge of said second ground plane to said first groundplane, respectively.
 14. The data processing terminal according to claim3, wherein three of said resistive connecting means connect positionsnear a center and both ends of an edge of said second ground plane tosaid first ground plane, respectively.
 15. The data processing terminalaccording to claim 3, wherein: said first ground plane is formed on aparent board which has said data processing circuit mounted thereon;said second ground plane is formed on a child board which has a memorycircuit mounted thereon for temporarily storing data processed by saiddata processing circuit; said resistive connecting means comprises aresistor mounted on said parent board and connected to said first groundplane; and said resistor on said parent board is connected to saidsecond ground plane on said child board through a conductor.
 16. Thedata processing terminal according to claim 3, wherein: said firstground plane is formed on a parent board which has said data processingcircuit mounted thereon; said second ground plane is formed on a childboard which has a memory circuit mounted thereon for temporarily storingdata processed by said data processing circuit; said resistiveconnecting means comprises a resistor mounted on said child board andconnected to said second ground plane; and said resistor on said childboard is connected to said first ground plane on said parent boardthrough a conductor.
 17. The data processing terminal according to claim3, wherein: said first ground plane is formed on a parent board whichhas said data processing circuit mounted thereon; said second groundplane is formed on a child board which has a memory circuit mountedthereon for temporarily storing data processed by said data processingcircuit; said resistive connecting means comprises two resistors, one ofsaid resistors being mounted on said parent board and connected to saidfirst ground plane, and the other of said resistors being mounted onsaid child board and connected to said second ground plane; and saidresistors on said parent board and said child board are connected toeach other through a conductor.
 18. The data processing terminalaccording to claim 3, further comprising a radio communication circuitremovably mounted therein for making radio communications with theoutside; wherein said radio communication circuit is in wiredcommunication with said data processing circuit.
 19. The data processingterminal according to claim 3, further comprising: a radio communicationcircuit formed integrally therewith for making radio communications withthe outside; wherein said radio communication circuit is in wiredcommunication with said data processing circuit.
 20. The data processingterminal according to claim 1, wherein one of said resistive connectingmeans connects a position near a center of an edge of said second groundplane to said first ground plane.
 21. The data processing terminalaccording to claim 20, wherein: said resistive connecting means isformed in an elongated shape having an overall length equivalent to anedge of said second ground plane; and said resistive connecting means ispositioned substantially in parallel with the edge of said second groundplane.
 22. The data processing terminal according to claim 20, wherein:said first ground plane is formed on a parent board which has said dataprocessing circuit mounted thereon; said second ground plane is formedon a child board which has a memory circuit mounted thereon fortemporarily storing data processed by said data processing circuit; saidresistive connecting means comprises a resistor mounted on said parentboard and connected to said first ground plane; and said resistor onsaid parent board is connected to said second ground plane on said childboard through a conductor.
 23. The data processing terminal according toclaim 20, wherein: said first ground plane is formed on a parent boardwhich has said data processing circuit mounted thereon; said secondground plane is formed on a child board which has a memory circuitmounted thereon for temporarily storing data processed by said dataprocessing circuit; said resistive connecting means comprises a resistormounted on said child board and connected to said second ground plane;and said resistor on said child board is connected to said first groundplane on said parent board through a conductor.
 24. The data processingterminal according to claim 20, wherein: said first ground plane isformed on a parent board which has said data processing circuit mountedthereon; said second ground plane is formed on a child board which has amemory circuit mounted thereon for temporarily storing data processed bysaid data processing circuit; said resistive connecting means comprisestwo resistors, one of said resistors being mounted on said parent boardand connected to said first ground plane, and the other of saidresistors being mounted on said child board and connected to said secondground plane; and said resistors on said parent board and said childboard are connected to each other through a conductor.
 25. The dataprocessing terminal according to claim 20, further comprising a radiocommunication circuit removably mounted therein for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 26.The data processing terminal according to claim 20, further comprising:a radio communication circuit formed integrally therewith for makingradio communications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 27.The data processing terminal according to claim 21, wherein: said firstground plane is formed on a parent board which has said data processingcircuit mounted thereon; said second ground plane is formed on a childboard which has a memory circuit mounted thereon for temporarily storingdata processed by said data processing circuit; said resistiveconnecting means comprises a resistor mounted on said parent board andconnected to said first ground plane; and said resistor on said parentboard is connected to said second ground plane on said child boardthrough a conductor.
 28. The data processing terminal according to claim21, wherein: said first ground plane is formed on a parent board whichhas said data processing circuit mounted thereon; said second groundplane is formed on a child board which has a memory circuit mountedthereon for temporarily storing data processed by said data processingcircuit; said resistive connecting means comprises a resistor mounted onsaid child board and connected to said second ground plane; and saidresistor on said child board is connected to said first ground plane onsaid parent board through a conductor.
 29. The data processing terminalaccording to claim 21, wherein: said first ground plane is formed on aparent board which has said data processing circuit mounted thereon;said second ground plane is formed on a child board which has a memorycircuit mounted thereon for temporarily storing data processed by saiddata processing circuit; said resistive connecting means comprises tworesistors, one of said resistors being mounted on said parent board andconnected to said first ground plane, and the other of said resistorsbeing mounted on said child board and connected to said second groundplane; and said resistors on said parent board and said child board areconnected to each other through a conductor.
 30. The data processingterminal according to claim 21, further comprising a radio communicationcircuit removably mounted therein for making radio communications withthe outside; wherein said radio communication circuit is in wiredcommunication with said data processing circuit.
 31. The data processingterminal according to claim 21, further comprising: a radiocommunication circuit formed integrally therewith for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 32.The data processing terminal according to claim 1, wherein two of saidresistive connecting means connect positions near both ends of an edgeof said second ground plane to said first ground plane, respectively.33. The data processing terminal according to claim 32, wherein: saidfirst ground plane is formed on a parent board which has said dataprocessing circuit mounted thereon; said second ground plane is formedon a child board which has a memory circuit mounted thereon fortemporarily storing data processed by said data processing circuit; saidresistive connecting means comprises a resistor mounted on said parentboard and connected to said first ground plane; and said resistor onsaid parent board is connected to said second ground plane on said childboard through a conductor.
 34. The data processing terminal according toclaim 32, wherein: said first ground plane is formed on a parent boardwhich has said data processing circuit mounted thereon; said secondground plane is formed on a child board which has a memory circuitmounted thereon for temporarily storing data processed by said dataprocessing circuit; said resistive connecting means comprises a resistormounted on said child board and connected to said second ground plane;and said resistor on said child board is connected to said first groundplane on said parent board through a conductor.
 35. The data processingterminal according to claim 32, wherein: said first ground plane isformed on a parent board which has said data processing circuit mountedthereon; said second ground plane is formed on a child board which has amemory circuit mounted thereon for temporarily storing data processed bysaid data processing circuit; said resistive connecting means comprisestwo resistors, one of said resistors being mounted on said parent boardand connected to said first ground plane, and the other of saidresistors being mounted on said child board and connected to said secondground plane; and said resistors on said parent board and said childboard are connected to each other through a conductor.
 36. The dataprocessing terminal according to claim 32, further comprising, a radiocommunication circuit removably mounted therein for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 37.The data processing terminal according to claim 32, further comprising:a radio communication circuit formed integrally therewith for makingradio communications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 38.The data processing terminal according to claim 1, wherein three of saidresistive connecting means connect positions near a center and both endsof an edge of said second ground plane to said first ground plane,respectively.
 39. The data processing terminal according to claim 38,wherein: said first ground plane is formed on a parent board which hassaid data processing circuit mounted thereon; said second ground planeis formed on a child board which has a memory circuit mounted thereonfor temporarily storing data processed by said data processing circuit;said resistive connecting means comprises a resistor mounted on saidparent board and connected to said first ground plane; and said resistoron said parent board is connected to said second ground plane on saidchild board through a conductor.
 40. The data processing terminalaccording to claim 38, wherein: said first ground plane is formed on aparent board which has said data processing circuit mounted thereon;said second ground plane is formed on a child board which has a memorycircuit mounted thereon for temporarily storing data processed by saiddata processing circuit; said resistive connecting means comprises aresistor mounted on said child board and connected to said second groundplane; and said resistor on said child board is connected to said firstground plane on said parent board through a conductor.
 41. The dataprocessing terminal according to claim 38, wherein: said first groundplane is formed on a parent board which has said data processing circuitmounted thereon; said second ground plane is formed on a child boardwhich has a memory circuit mounted thereon for temporarily storing dataprocessed by said data processing circuit; said resistive connectingmeans comprises two resistors, one of said resistors being mounted onsaid parent board and connected to said first ground plane, and theother of said resistors being mounted on said child board and connectedto said second ground plane; and said resistors on said parent board andsaid child board are connected to each other through a conductor. 42.The data processing terminal according to claim 38, further comprising aradio communication circuit removably mounted therein for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 43.The data processing terminal according to claim 38, further comprising:a radio communication circuit formed integrally therewith for makingradio communications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 44.The data processing terminal according to claim 1, wherein: said firstground plane is formed on a parent board which has said data processingcircuit mounted thereon; said second ground plane is formed on a childboard which has a memory circuit mounted thereon for temporarily storingdata processed by said data processing circuit; said resistiveconnecting means comprises a resistor mounted on said parent board andconnected to said first ground plane; and said resistor on said parentboard is connected to said second ground plane on said child boardthrough a conductor.
 45. The data processing terminal according to claim44, further comprising: a radio communication circuit formed integrallytherewith for making radio communications with the outside; wherein saidradio communication circuit is in wired communication with said dataprocessing circuit.
 46. A parent board for the data processing terminalaccording to claim 44, comprising: said first ground plane formedthereon; and said resistor mounted thereon and connected to said firstground plane to serve as said resistive connecting means.
 47. The dataprocessing terminal according to claim 44, further comprising a radiocommunication circuit removably mounted therein for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 48.The data processing terminal according to claim 1, wherein: said firstground plane is formed on a parent board which has said data processingcircuit mounted thereon; said second ground plane is formed on a childboard which has a memory circuit mounted thereon for temporarily storingdata processed by said data processing circuit; said resistiveconnecting means comprises a resistor mounted on said child board andconnected to said second ground plane; and said resistor on said childboard is connected to said first ground plane on said parent boardthrough a conductor.
 49. The data processing terminal according to claim48, further comprising a radio communication circuit removably mountedtherein for making radio communications with the outside; wherein saidradio communication circuit is in wired communication with said dataprocessing circuit.
 50. The data processing terminal according to claim48, further comprising: a radio communication circuit formed integrallytherewith for making radio communications with the outside; wherein saidradio communication circuit is in wired communication with said dataprocessing circuit.
 51. A child board for the data processing terminalaccording to claim 48, comprising: said second ground plane formedthereon; and said resistor mounted thereon and connected to said secondground plane to serve as said resistive connecting means.
 52. The dataprocessing terminal according to claim 1, wherein: said first groundplane is formed on a parent board which has said data processing circuitmounted thereon; said second ground plane is formed on a child boardwhich has a memory circuit mounted thereon for temporarily storing dataprocessed by said data processing circuit; said resistive connectingmeans comprises two resistors, one of said resistors being mounted onsaid parent board and connected to said first ground plane, and theother of said resistors being mounted on said child board and connectedto said second ground plane; and said resistors on said parent board andsaid child board are connected to each other through a conductor. 53.The data processing terminal according to claim 52, further comprising aradio communication circuit removably mounted therein for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 54.The data processing terminal according to claim 52, further comprising:a radio communication circuit formed integrally therewith for makingradio communications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 55.The data processing terminal according to claim 1, further comprising aradio communication circuit removably mounted therein for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit. 56.The data processing terminal according to claim 1, further comprising: aradio communication circuit formed integrally therewith for making radiocommunications with the outside; wherein said radio communicationcircuit is in wired communication with said data processing circuit.